Porous metals and metal-carbon composites with nanoscale dimensions of struts or pore walls have a number of current and potential applications. For example, nanostructured Au could be used for molecular detectors and sensors or as a catalyst; Pd is attractive for hydrogen gas sensors; Cu and Ag nanoparticles are of interest to applications capitalizing on their antimicrobial and bactericidal activity. Other nanostructured metals (such as Ru, Pt, and Ni) and metal oxides (such as MnO2, Co3O4, Cu2O, NiO, and RuO2) are attractive for energy storage devices. Nanoporous metal-carbon composites could capitalize on the large surface areas and attractive mechanical properties of the nanoporous carbon scaffold and the functionalities of metal nanoparticles. Moreover, ultralow density (<50 mg/cm3) nanostructured porous metals are attractive as targets for ultrabright x-ray sources.
Although a number of methods have been proposed to form different metal-CNT composites, little has been done to fabricate macroscopically sized three-dimensional metal-carbon composites with controlled dimensions, density, composition, pore size distributions, and mechanical properties. The sol-gel approach is commonly used to synthesize monolithic nanoporous carbons. For metal-carbon composites, however, it is challenging to achieve both high metal loading and low monolith densities. Thus, a need exists for new nanoporous metal-carbon composites with tunable properties and methods for making them.